Corrugated plastic pipe, in for example 250 foot lengths is widely used for the drainage of agricultural lands, joined lengths of pipe, being buried in a grid pattern and extending thousands of feet under the plot of land to be drained. Joining the lengths of pipe has, however, presented a problem. In view of the stresses in the individual lengths of pipe, a freely rotating (swivel) coupling is preferably so that the stresses in one pipe are not transmitted to the pipe to which it is coupled. For free rotation, the coupling provides at least one annular rib projecting radially outwardly from the outer surface of a male component, and a like number of annular grooves formed to extend radially outwardly from the inner surface of the female component. When the lengths of pipe are joined, the rib swivels in the annular groove, and is retained therein because the at least one annular rib has a greater diameter than the inner surface wall of the female component. In this manner, any twisting of one pipe in the chain causes the one component to freely rotate with respect to the other component, thereby minimizing the effect on the total length of pipe joined.
While this coupling is very effective in achieving the desired result, the joining of the components to provide this end coupling is very difficult. Pushing the two components axially together is not very feasible, because of the relative dimensions of the annular rib and inner surface wall of the female components.
In the past, the female component of the coupling was cut and opened, the male component positioned in the female component and the female component wrapped securely around the male component so that each annular rib projects into the groove. The two components were then tied together with wire. The results however, were not completely satisfactory since the cutting and tying procedure requiring additional labour, and through years of burial in the ground, the wire tended to corrode and the joint weakened.
It is therefore, an object of this invention to provide a more satisfactory coupling which eliminates the need for cutting and reduces the stress of coupling the components together, while at the same time, provides for maximum coupling effectiveness.
Further and other objects of the invention will be realized by those skilled in the art from the following summary of the invention and detailed description of the preferred embodiments thereof.